#12400 NORM 13.2.0: Determine MMP3 audio buffer parameters

Zarro Boogs per Child bugtracker at laptop.org
Tue Apr 16 15:27:58 EDT 2013

#12400: Determine MMP3 audio buffer parameters
           Reporter:  dsd      |       Owner:  saadia       
               Type:  defect   |      Status:  new          
           Priority:  normal   |   Milestone:  13.2.0       
          Component:  kernel   |     Version:  not specified
         Resolution:           |    Keywords:               
        Next_action:  package  |    Verified:  0            
Deployment_affected:           |   Blockedby:               
           Blocking:  12343    |  
Changes (by dsd):

 * cc: Quozl (added)


 James, please add the following equivalent code to OFW:

 dev /pcm at 0
 d# 63488 encode-int
 d# 2048 encode-int encode+
 d# 63488 encode-int encode+
 d# 2048 encode-int encode+
 " marvell,buffer-sizes" property

 Rationale for the values:

 The /asram node (via its 'reg' property) defines that 128kb of SRAM is
 assigned to the audio functionality. We now divide that here, roughly half
 to playback and half to recording.

 Even though we choose big buffers, we do leave a little bit of free space
 for the DMA engine which also needs to use a bit of the SRAM area for DMA
 descriptors. Therefore we choose 62kb for each buffer, leaving 4kb
 available for DMA descriptors.

 For the max period size, we don't have any justification other than 2048
 is the value we've been using all along.

Ticket URL: <http://dev.laptop.org/ticket/12400#comment:13>
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